1. Technical Field
Embodiments relate to RC-type oscillator circuits used for generating clock signals, for example pulsed-type signals. Particularly, embodiments relate to oscillator circuits formed by an integrated electronic circuit in a chip made of a semiconductor material.
2. Discussion of the Related Art
RC-type oscillator circuits formed by an integrated circuit made of a semiconductor material, capable of generating a clock signal, using internal resistors and capacitors, that is integrated in the same chip, are known. Such RC-type oscillators neither use inner or outer inductors nor outer crystals. In the automotive field, the RC oscillators are used in the electronic systems in order to generate frequencies in the range of 100 kHz-100 MHz.
Document US-A-2010/0013566 describes a RC-type oscillator comprising a resistor and two capacitors. The two capacitors are alternatively charged by currents generated by a current mirror and are alternatively discharged. The RC oscillator circuit, described in this document, is provided with a sensing unit generating an impulse of the clock signal each time the voltage across one of the two capacitors exceeds a logic threshold level.
Referring to the known RC oscillators, the Applicant has observed that the generated clock experiences an undesired frequency shift with respect to a project nominal value. This undesired translation is for example caused by the manufacturing process of the corresponding integrated circuit. Particularly, the Applicant has noted that a first contribution to the frequency shift is present in the circuit integrated in the silicon die (in the wafer state) before the step of packaging the die itself. This contribution can be generally compensated by a process of calibrating the circuit itself.
Whereas, a second contribution to the frequency shift is determined by mechanical stresses associated with the steps of cutting the silicon die from the wafer and with the following packaging step. The compensation of this second contribution, for example by a further step of calibrating the circuit provided with a package, apart from being complex and expensive, could be disappointing.